Downlink control channel monitoring

ABSTRACT

Various communication systems may benefit from the appropriate monitoring of communication channels. For example, certain wireless communication systems may benefit from downlink control channel monitoring optimized for discontinuous reception mode and/or narrowband operation. A method can include selecting a search space configuration from a plurality of search space configurations for a user equipment. The method can also include operating the user equipment in the selected search space configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 16/475,564, filed Jul. 2, 2019 and entitled“Downlink Control Channel Monitoring,” which is a National Stage Entryof International Application Serial No. PCT/IB2018/050024, filed Jan. 2,2018 and entitled “Downlink Control Channel Monitoring Optimizing forDiscontinuous Reception Mode and/or Narrowband Operation,” which claimspriority to and the benefit of, U.S. Provisional Application Ser. No.62/442,693, filed Jan. 5, 2017 and entitled “Downlink Control ChannelMonitoring,” the entire disclosures of each of which are herebyincorporated herein by reference in their entireties for all purposes.

FIELD

Various communication systems may benefit from the appropriatemonitoring of communication channels. For example, certain wirelesscommunication systems may benefit from downlink control channelmonitoring optimized for discontinuous reception mode and/or narrowbandoperation.

BACKGROUND

FIG. 1 illustrates exemplary slot types in new radio (NR). Moreparticularly, FIG. 1 shows a frame structure that can be applied in NR.The slot length, as well as the portion of the orthogonal frequencydivision multiplexed (OFDM) symbols reserved for downlink (DL) control,DL data, guard period, uplink (UL) data and UL control as well as cyclicprefix (not shown in the figure) length may vary according toscenario/use case. There are three slot types shown in FIG. 1 . Thesethree slot types provide the basic support for both time division duplex(TDD) and frequency division duplex (FDD). NR may strive for efficientsupport of dynamic resource allocation of different numerologies infrequency division multiplexed (FDM)/time division multiplexed (TDM)fashion.

For the bi-directional slots, there is either downlink data or uplinkdata transmission in each slot, as well as the corresponding downlinkand uplink control. Bi-directional slot facilitates many TDDfunctionalities in the NR frame structure, such as link directionswitching between DL and UL; fully flexible traffic adaptation betweenDL and UL; and opportunity for low latency, provided that slot length isselected to be short enough.

In all slots, multiplexing among DL control, DL/UL data, GP and ULcontrol is based primarily on time division multiplexing allowing fastenergy efficient pipeline processing of control and data in thereceiver. Physical downlink control channel (PDCCH) is conveyed in theDL control symbol(s) located at the beginning of the slot.

In addition to bi-directional slots, there are also DL slots and ULslots in FIG. 1 . These are needed at least in FDD mode, but also incertain TDD scenarios to allow longer transmission periods in the samedirection.

FIG. 2 illustrates an example arrangement for PDCCH search spacesincluding also control channel element (CCE) allocation for the commonsearch space (CSS). In LTE, (enhanced) PDCCH ((E)PDCCH) carries downlinkcontrol information (DCI), which includes resource assignment and othercontrol information for a user equipment (UE) or group of UEs. EachPDCCH is transmitted using one or more control channel elements (CCE).Different PDCCH sizes with different CCE aggregation levels (e.g.,comprising 1, 2, 4 or 8 CCEs) are supported in LTE Rel-8.

In LTE, UE needs to decode all possible PDCCH sizes and locations inorder to act on those messages with correct cyclic redundancy code (CRC)scrambled with a UE identity. Carrying out such blind decoding of allpossible combinations (of PDCCH sizes and locations) in every subframemay lead to excessive power consumption and processing time requirementsat the UE side as well as increased probability of false UL/DL grantdetection. In order to limit the number of blind decoding attempts, LTEsystem has adopted an approach in which only a limited set of CCElocations where a PDCCH may be placed is defined for each UE. Thisprocessing reduction is made at the expense of PDCCH schedulingflexibility. The limited CCE set is considered as a PDCCH search space,which is divided into common part with 6 PDCCH candidates and dedicatedpart with 16 candidates, respectively. These candidates need to bedecoded twice as there are two size options defined for the PDCCH bothin common and in dedicated search space. This gives the maximum numberof PDCCH blind decoding attempts (=44), which the LTE Rel-8 UE isrequired to carry out in any subframe. UE's PDCCH blind detectioncapability increases linearly with the number of DL CCs supported in LTECarrier aggregation (i.e., Rel-10 and beyond).

PDCCH structure including search space design in NR is completely openin third generation partnership project (3GPP). However, there may betwo types of search spaces, common search space (CSS) and user-specificsearch space (USS). They can be arranged in the frequency domain forexample according to the following principles: next generation NodeB(gNB) can configure both CSS and USS in a flexible manner in frequency;CSS may always be located in the first OFDM symbol of the slot (or inthe case of narrowband operation requiring a high number of CCEs, suchas 8, CSS may be located within first two OFDM symbols of the slot); andUSS may have more flexibility in time. For example, USS may cover one ormore OFDM symbols at the beginning of the slot, or USS may be located inthe first symbol of the mini-slot. Configuration can be done accordingto a 4 physical resource block (PRB) raster. CCE size can be 4 PRBs inone orthogonal frequency division multiplexed (OFDM) symbolcorresponding to 48 subcarriers (4×12 subcarriers).

Both localized and distributed CCEs are supported. Localized CCE can bemade up of four consecutive PRBs within a 4-PRB raster. In the exampleof FIG. 2 , USS follows localized CCE allocation. Distributed PRBs canbe allocated in 4-CCE groups. In the example of FIG. 2 , CSS followsdistributed CCE allocation.

FIG. 3 illustrates distribution of daily UE modem power consumption for20 MHz, as explained in R1-1609557. PDCCH blind detection can be seen asa considerable burden for the UE. According to R1-1609557, around 64% ofdaily UE power consumption is occupied by PDCCH-only and low data rateservices, as shown in FIG. 3 .

There are some techniques to reduce the power consumption by PDCCH onlyand low data rate services. These include, for example, improvedmicro-sleep and dynamic bandwidth adaptation based on traffic needs.While (E)PDCCH blind detection techniques may address some issues, ascan be seen from FIG. 3 significant improvement may still be needed.

BRIEF SUMMARY

Described herein are systems, methods, apparatuses, and computer programproducts for downlink control channel monitoring.

In some embodiments, a method can be carried out that includes selectinga search space configuration from a plurality of search spaceconfigurations for a user equipment; and operating the user equipment inthe selected search space configuration, wherein the plurality of searchspace configurations can respectively cover at least two differentbandwidths. In some embodiments, the method can further compriseswitching between search space configurations. In some embodiments, theselecting is based on at least one of need for bandwidth or based on anexplicit indication from an access node. In some embodiments, theswitching is based on at least one of a change in need for bandwidth, anexpiration of a timer, or an explicit indication from an access node.

In some embodiments, the switching comprises switching fromconfiguration A to configuration B or switching from configuration B toconfiguration A. In some embodiments, the method can further compriserelying on a timer when switching from the configuration A to theconfiguration B, or relying on an additional synchronization signal whenswitching from the configuration B to the configuration A. In someembodiments, the configuration A comprises one or more of the followingattributes: search space(s) covering a wide bandwidth; search space(s)covering a high number of control channel elements; user equipmentoperating with a high number of physical downlink control channel blinddecoding attempts per slot or per mini-slot or per subframe; userequipment monitoring all required physical downlink control channel fromboth slots and mini-slots; user equipment operating with radio frequencybandwidth up to a bandwidth corresponding to maximum channel bandwidth;or user equipment having a large data volume in at least one linkdirection, either downlink or uplink. In some embodiments, theconfiguration B comprises one or more of the following attributes:search space(s) covering a narrow bandwidth; search space(s) covering alow number of control channel elements; user equipment operating with alow number of physical downlink control channel blind decoding; userequipment monitoring physical downlink control channel at maximum withslot resolution at least in discontinuous reception mode; user equipmentoperating with radio frequency bandwidth corresponding to a subset ofthe maximum channel bandwidth; or user equipment supporting a limiteddata volume in at least in at least one link direction, either downlinkor uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the method can further comprise receiving configuration ofthe plurality search space configurations by higher layer signaling. Insome embodiments, the plurality of search space configurations compriseat least one of a first search space configuration configured to causethe user equipment to follow all physical downlink control channelaggregation levels, a second search space configuration configured tocause the user equipment to follow only a subset of physical downlinkcontrol channel aggregation levels, a first search space configurationconfigured to cause the user equipment to follow both a common searchspace and a user specific search space, a second search spaceconfiguration configured to cause the user equipment to follow only acommon search space, or different user specific search spaces from oneanother. In some embodiments, the operating of the user equipmentcomprises performing physical downlink control channel blind detection.

According to other embodiments, a method can comprise selecting a searchspace configuration from a plurality of search space configurations fora user equipment; and indicating to the user equipment the selectedsearch space configuration, wherein the plurality of search spaceconfigurations respectively cover at least two different bandwidths. Insome embodiments, the method can further comprise sending an indicationto the user equipment to switch to a different search spaceconfiguration of the plurality of search space configurations. In someembodiments, the selecting is based on at least one of need forbandwidth. In some embodiments, the switching is based on at least oneof a change in need for bandwidth, the expiration of a timer.

In some embodiments, the switching comprises switching fromconfiguration A to configuration B or switching from configuration B toconfiguration A. In some embodiments, the method further comprisesrelying on a timer when switching from the configuration A to theconfiguration B, or relying on an additional synchronization signal whenswitching from the configuration B to the configuration A. In someembodiments, the configuration A comprises one or more of the followingattributes: search space(s) covering a wide bandwidth; search space(s)covering a high number of control channel elements; user equipmentoperating with a high number of physical downlink control channel blinddecoding attempts per slot or per mini-slot or per subframe; userequipment monitoring all required physical downlink control channel fromboth slots and mini-slots; user equipment operating with radio frequencybandwidth up to a bandwidth corresponding to maximum channel bandwidth;or user equipment having a large data volume in at least one linkdirection, either downlink or uplink. In some embodiments, theconfiguration B comprises one or more of the following attributes:search space(s) covering a narrow bandwidth; search space(s) covering alow number of control channel elements; user equipment operating with alow number of physical downlink control channel blind decoding; userequipment monitoring physical downlink control channel at maximum withslot resolution at least in discontinuous reception mode; user equipmentoperating with radio frequency bandwidth corresponding to a subset ofthe maximum channel bandwidth; or user equipment supporting a limiteddata volume in at least in at least one link direction, either downlinkor uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the plurality of search space configurations comprise atleast one of a first search space configuration configured to cause theuser equipment to follow all physical downlink control channelaggregation levels, a second search space configuration configured tocause the user equipment to follow only a subset of physical downlinkcontrol channel aggregation levels, a first search space configurationconfigured to cause the user equipment to follow both a common searchspace and a user specific search space, a second search spaceconfiguration configured to cause the user equipment to follow only acommon search space, or different user specific search spaces from oneanother.

According to other embodiments, an apparatus can be provided thatcomprises means for performing a method such as described above orelsewhere herein. For example, the apparatus can comprise means forselecting a search space configuration from a plurality of search spaceconfigurations for a user equipment; and means for operating the userequipment in the selected search space configuration, wherein theplurality of search space configurations can respectively cover at leasttwo different bandwidths. In some embodiments, the method can furthercomprise switching between search space configurations. In someembodiments, the selecting is based on at least one of need forbandwidth or based on an explicit indication from an access node. Insome embodiments, the switching is based on at least one of a change inneed for bandwidth, an expiration of a timer, or an explicit indicationfrom an access node.

In some embodiments, the means for switching comprises means forswitching from configuration A to configuration B or switching fromconfiguration B to configuration A. In some embodiments, the apparatuscan further comprise means for relying on a timer when switching fromthe configuration A to the configuration B, or relying on an additionalsynchronization signal when switching from the configuration B to theconfiguration A. In some embodiments, the configuration A comprises oneor more of the following attributes: search space(s) covering a widebandwidth; search space(s) covering a high number of control channelelements; user equipment operating with a high number of physicaldownlink control channel blind decoding attempts per slot or permini-slot or per subframe; user equipment monitoring all requiredphysical downlink control channel from both slots and mini-slots; userequipment operating with radio frequency bandwidth up to a bandwidthcorresponding to maximum channel bandwidth; or user equipment having alarge data volume in at least one link direction, either downlink oruplink. In some embodiments, the configuration B comprises one or moreof the following attributes: search space(s) covering a narrowbandwidth; search space(s) covering a low number of control channelelements; user equipment operating with a low number of physicaldownlink control channel blind decoding; user equipment monitoringphysical downlink control channel at maximum with slot resolution atleast in discontinuous reception mode; user equipment operating withradio frequency bandwidth corresponding to a subset of the maximumchannel bandwidth; or user equipment supporting a limited data volume inat least in at least one link direction, either downlink or uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the apparatus can further comprise means for receivingconfiguration of the plurality search space configurations by higherlayer signaling. In some embodiments, the plurality of search spaceconfigurations comprise at least one of a first search spaceconfiguration configured to cause the user equipment to follow allphysical downlink control channel aggregation levels, a second searchspace configuration configured to cause the user equipment to followonly a subset of physical downlink control channel aggregation levels, afirst search space configuration configured to cause the user equipmentto follow both a common search space and a user specific search space, asecond search space configuration configured to cause the user equipmentto follow only a common search space, or different user specific searchspaces from one another. In some embodiments, the operating of the userequipment comprises performing physical downlink control channel blinddetection.

According to other embodiments, an apparatus can be provided thatcomprises means for performing a method such as described above orelsewhere herein. For example, the apparatus can comprise means forselecting a search space configuration from a plurality of search spaceconfigurations for a user equipment; and means for indicating to theuser equipment the selected search space configuration, wherein theplurality of search space configurations respectively cover at least twodifferent bandwidths. In some embodiments, the apparatus can furthercomprise means for sending an indication to the user equipment to switchto a different search space configuration of the plurality of searchspace configurations. In some embodiments, the means for selectingcomprises means for selecting based on at least one of need forbandwidth. In some embodiments, the means for switching comprises meansfor switching based on at least one of a change in need for bandwidth orthe expiration of a timer.

In some embodiments, the means for switching comprises means forswitching from configuration A to configuration B or switching fromconfiguration B to configuration A. In some embodiments, the apparatusfurther comprises means for relying on a timer when switching from theconfiguration A to the configuration B, or relying on an additionalsynchronization signal when switching from the configuration B to theconfiguration A. In some embodiments, the configuration A comprises oneor more of the following attributes: search space(s) covering a widebandwidth; search space(s) covering a high number of control channelelements; user equipment operating with a high number of physicaldownlink control channel blind decoding attempts per slot or permini-slot or per subframe; user equipment monitoring all requiredphysical downlink control channel from both slots and mini-slots; userequipment operating with radio frequency bandwidth up to a bandwidthcorresponding to maximum channel bandwidth; or user equipment having alarge data volume in at least one link direction, either downlink oruplink. In some embodiments, the configuration B comprises one or moreof the following attributes: search space(s) covering a narrowbandwidth; search space(s) covering a low number of control channelelements; user equipment operating with a low number of physicaldownlink control channel blind decoding; user equipment monitoringphysical downlink control channel at maximum with slot resolution atleast in discontinuous reception mode; user equipment operating withradio frequency bandwidth corresponding to a subset of the maximumchannel bandwidth; or user equipment supporting a limited data volume inat least in at least one link direction, either downlink or uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the plurality of search space configurations comprise atleast one of a first search space configuration configured to cause theuser equipment to follow all physical downlink control channelaggregation levels, a second search space configuration configured tocause the user equipment to follow only a subset of physical downlinkcontrol channel aggregation levels, a first search space configurationconfigured to cause the user equipment to follow both a common searchspace and a user specific search space, a second search spaceconfiguration configured to cause the user equipment to follow only acommon search space, or different user specific search spaces from oneanother.

According to other embodiments, an apparatus can be provided thatcomprises at least one processor and at least one memory includingcomputer program code. In some embodiments, the at least one memory andthe computer program code can be configured to, with the at least oneprocessor, cause the apparatus at least to perform a method such asdescribed above or elsewhere herein. For example, the at least onememory and the computer program code can be configured to, with the atleast one processor, cause the apparatus at least to perform selecting asearch space configuration from a plurality of search spaceconfigurations for a user equipment; and operating the user equipment inthe selected search space configuration, wherein the plurality of searchspace configurations can respectively cover at least two differentbandwidths. In some embodiments, the at least one memory and thecomputer program code can be further configured to, with the at leastone processor, cause the apparatus at least to perform switching betweensearch space configurations. In some embodiments, the selecting is basedon at least one of need for bandwidth or based on an explicit indicationfrom an access node. In some embodiments, the switching is based on atleast one of a change in need for bandwidth, an expiration of a timer,or an explicit indication from an access node.

In some embodiments, the at least one memory and the computer programcode can be further configured to, with the at least one processor,cause the apparatus at least to perform the switching by switching fromconfiguration A to configuration B or switching from configuration B toconfiguration A. In some embodiments, the at least one memory and thecomputer program code can be configured to, with the at least oneprocessor, cause the apparatus at least to perform relying on a timerwhen switching from the configuration A to the configuration B, orrelying on an additional synchronization signal when switching from theconfiguration B to the configuration A. In some embodiments, theconfiguration A comprises one or more of the following attributes:search space(s) covering a wide bandwidth; search space(s) covering ahigh number of control channel elements; user equipment operating with ahigh number of physical downlink control channel blind decoding attemptsper slot or per mini-slot or per subframe; user equipment monitoring allrequired physical downlink control channel from both slots andmini-slots; user equipment operating with radio frequency bandwidth upto a bandwidth corresponding to maximum channel bandwidth; or userequipment having a large data volume in at least one link direction,either downlink or uplink. In some embodiments, the configuration Bcomprises one or more of the following attributes: search space(s)covering a narrow bandwidth; search space(s) covering a low number ofcontrol channel elements; user equipment operating with a low number ofphysical downlink control channel blind decoding; user equipmentmonitoring physical downlink control channel at maximum with slotresolution at least in discontinuous reception mode; user equipmentoperating with radio frequency bandwidth corresponding to a subset ofthe maximum channel bandwidth; or user equipment supporting a limiteddata volume in at least in at least one link direction, either downlinkor uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the at least one memory and the computer program code canbe configured to, with the at least one processor, cause the apparatusat least to perform receiving configuration of the plurality searchspace configurations by higher layer signaling. In some embodiments, theplurality of search space configurations comprise at least one of afirst search space configuration configured to cause the user equipmentto follow all physical downlink control channel aggregation levels, asecond search space configuration configured to cause the user equipmentto follow only a subset of physical downlink control channel aggregationlevels, a first search space configuration configured to cause the userequipment to follow both a common search space and a user specificsearch space, a second search space configuration configured to causethe user equipment to follow only a common search space, or differentuser specific search spaces from one another. In some embodiments, theoperating of the user equipment comprises performing physical downlinkcontrol channel blind detection.

According to other embodiments, an apparatus can be provided thatcomprises at least one processor and at least one memory storingcomputer program code, wherein the at least one memory and the computerprogram code can be configured to, with the at least one processor,cause the apparatus at least to perform a method such as described aboveor elsewhere herein. For example, the at least one memory and thecomputer program code can be configured to, with the at least oneprocessor, cause the apparatus at least to perform selecting a searchspace configuration from a plurality of search space configurations fora user equipment; and indicating to the user equipment the selectedsearch space configuration, wherein the plurality of search spaceconfigurations respectively cover at least two different bandwidths. Insome embodiments, the at least one memory and the computer program codecan be configured to, with the at least one processor, cause theapparatus at least to perform sending an indication to the userequipment to switch to a different search space configuration of theplurality of search space configurations. In some embodiments, theselecting comprises selecting based on at least one of need forbandwidth. In some embodiments, the switching comprises switching basedon at least one of a change in need for bandwidth or the expiration of atimer.

In some embodiments, the switching comprises switching fromconfiguration A to configuration B or switching from configuration B toconfiguration A. In some embodiments, the at least one memory and thecomputer program code can be configured to, with the at least oneprocessor, cause the apparatus at least to perform relying on a timerwhen switching from the configuration A to the configuration B, orrelying on an additional synchronization signal when switching from theconfiguration B to the configuration A. In some embodiments, theconfiguration A comprises one or more of the following attributes:search space(s) covering a wide bandwidth; search space(s) covering ahigh number of control channel elements; user equipment operating with ahigh number of physical downlink control channel blind decoding attemptsper slot or per mini-slot or per subframe; user equipment monitoring allrequired physical downlink control channel from both slots andmini-slots; user equipment operating with radio frequency bandwidth upto a bandwidth corresponding to maximum channel bandwidth; or userequipment having a large data volume in at least one link direction,either downlink or uplink. In some embodiments, the configuration Bcomprises one or more of the following attributes: search space(s)covering a narrow bandwidth; search space(s) covering a low number ofcontrol channel elements; user equipment operating with a low number ofphysical downlink control channel blind decoding; user equipmentmonitoring physical downlink control channel at maximum with slotresolution at least in discontinuous reception mode; user equipmentoperating with radio frequency bandwidth corresponding to a subset ofthe maximum channel bandwidth; or user equipment supporting a limiteddata volume in at least in at least one link direction, either downlinkor uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the plurality of search space configurations comprise atleast one of a first search space configuration configured to cause theuser equipment to follow all physical downlink control channelaggregation levels, a second search space configuration configured tocause the user equipment to follow only a subset of physical downlinkcontrol channel aggregation levels, a first search space configurationconfigured to cause the user equipment to follow both a common searchspace and a user specific search space, a second search spaceconfiguration configured to cause the user equipment to follow only acommon search space, or different user specific search spaces from oneanother.

According to other embodiments, a computer program product can beprovided that comprises instructions for performing a process includinga method such as described above or elsewhere herein. For example, theinstructions, when executed by a processor, can cause an apparatus atleast to select a search space configuration from a plurality of searchspace configurations for a user equipment; and operate the userequipment in the selected search space configuration, wherein theplurality of search space configurations can respectively cover at leasttwo different bandwidths. In some embodiments, the instructions, whenexecuted by a processor, can cause an apparatus at least to switchbetween search space configurations. In some embodiments, the selectingis based on at least one of need for bandwidth or based on an explicitindication from an access node. In some embodiments, the switching isbased on at least one of a change in need for bandwidth, an expirationof a timer, or an explicit indication from an access node.

In some embodiments, the instructions, when executed by a processor, cancause an apparatus at least to switch from configuration A toconfiguration B or switch from configuration B to configuration A. Insome embodiments, the instructions, when executed by a processor, cancause an apparatus at least to rely on a timer when switching from theconfiguration A to the configuration B, or rely on an additionalsynchronization signal when switching from the configuration B to theconfiguration A. In some embodiments, the configuration A comprises oneor more of the following attributes: search space(s) covering a widebandwidth; search space(s) covering a high number of control channelelements; user equipment operating with a high number of physicaldownlink control channel blind decoding attempts per slot or permini-slot or per subframe; user equipment monitoring all requiredphysical downlink control channel from both slots and mini-slots; userequipment operating with radio frequency bandwidth up to a bandwidthcorresponding to maximum channel bandwidth; or user equipment having alarge data volume in at least one link direction, either downlink oruplink. In some embodiments, the configuration B comprises one or moreof the following attributes: search space(s) covering a narrowbandwidth; search space(s) covering a low number of control channelelements; user equipment operating with a low number of physicaldownlink control channel blind decoding; user equipment monitoringphysical downlink control channel at maximum with slot resolution atleast in discontinuous reception mode; user equipment operating withradio frequency bandwidth corresponding to a subset of the maximumchannel bandwidth; or user equipment supporting a limited data volume inat least in at least one link direction, either downlink or uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the instructions, when executed by a processor, can causean apparatus at least to receive configuration of the plurality searchspace configurations by higher layer signaling. In some embodiments, theplurality of search space configurations comprise at least one of afirst search space configuration configured to cause the user equipmentto follow all physical downlink control channel aggregation levels, asecond search space configuration configured to cause the user equipmentto follow only a subset of physical downlink control channel aggregationlevels, a first search space configuration configured to cause the userequipment to follow both a common search space and a user specificsearch space, a second search space configuration configured to causethe user equipment to follow only a common search space, or differentuser specific search spaces from one another. In some embodiments, theoperating of the user equipment comprises performing physical downlinkcontrol channel blind detection.

According to other embodiments, a computer program product can beprovided that comprises instructions for performing a process includinga method such as described above or elsewhere herein. For example, theinstructions, when executed by a processor, can cause an apparatus atleast to select a search space configuration from a plurality of searchspace configurations for a user equipment; and indicate to the userequipment the selected search space configuration, wherein the pluralityof search space configurations respectively cover at least two differentbandwidths. In some embodiments, the instructions, when executed by aprocessor, can cause an apparatus at least to send an indication to theuser equipment to switch to a different search space configuration ofthe plurality of search space configurations. In some embodiments, theselecting comprises selecting based on at least one of need forbandwidth. In some embodiments, the switching comprises switching basedon at least one of a change in need for bandwidth or the expiration of atimer.

In some embodiments, the switching comprises switching fromconfiguration A to configuration B or switching from configuration B toconfiguration A. In some embodiments, the instructions, when executed bya processor, can cause an apparatus at least to rely on a timer whenswitching from the configuration A to the configuration B, or relying onan additional synchronization signal when switching from theconfiguration B to the configuration A. In some embodiments, theconfiguration A comprises one or more of the following attributes:search space(s) covering a wide bandwidth; search space(s) covering ahigh number of control channel elements; user equipment operating with ahigh number of physical downlink control channel blind decoding attemptsper slot or per mini-slot or per subframe; user equipment monitoring allrequired physical downlink control channel from both slots andmini-slots; user equipment operating with radio frequency bandwidth upto a bandwidth corresponding to maximum channel bandwidth; or userequipment having a large data volume in at least one link direction,either downlink or uplink. In some embodiments, the configuration Bcomprises one or more of the following attributes: search space(s)covering a narrow bandwidth; search space(s) covering a low number ofcontrol channel elements; user equipment operating with a low number ofphysical downlink control channel blind decoding; user equipmentmonitoring physical downlink control channel at maximum with slotresolution at least in discontinuous reception mode; user equipmentoperating with radio frequency bandwidth corresponding to a subset ofthe maximum channel bandwidth; or user equipment supporting a limiteddata volume in at least in at least one link direction, either downlinkor uplink.

In some embodiments, the plurality of search space configurationscomprise at least one of a first search space configuration configuredto support the user equipment in active data transmission, a secondsearch space configuration configured to support the user equipment indiscontinuous reception mode or in a low data rate service mode. In someembodiments, the plurality of search space configurations comprise atleast one of a first search space configuration configured to cause theuser equipment to follow all physical downlink control channelaggregation levels, a second search space configuration configured tocause the user equipment to follow only a subset of physical downlinkcontrol channel aggregation levels, a first search space configurationconfigured to cause the user equipment to follow both a common searchspace and a user specific search space, a second search spaceconfiguration configured to cause the user equipment to follow only acommon search space, or different user specific search spaces from oneanother.

BRIEF DESCRIPTION OF THE DRAWINGS

For proper understanding of the invention, reference should be made tothe accompanying drawings, wherein:

FIG. 1 illustrates slot types in new radio (NR).

FIG. 2 illustrates an example arrangement for PDCCH search spacesincluding also CCE allocation for the CSS.

FIG. 3 illustrates distribution of daily UE modem power consumption for20 MHz, e.g., as explained in R1-1609557.

FIG. 4 illustrates examples of common search space/user specific searchspace configurations for configuration A and configuration B, accordingto certain embodiments.

FIG. 5 illustrates a method according to certain embodiments.

FIG. 6 illustrates a system according to certain embodiments.

DETAILED DESCRIPTION

Certain embodiments relate to 3GPP New Radio (NR) physical layer designand related 3GPP study item (SI), RP-160671, although embodiments arenot limited to these examples. An objective of the SI is to identify anddevelop technology components needed for NR systems being able to useany spectrum band ranging at least up to 100 GHz. The goal is to achievea single technical framework addressing all usage scenarios,requirements, and deployment scenarios defined in 3GPP TR 38.913.

Certain embodiments more particularly relate to conveying downlinkcontrol information (DCI) within an NR carrier. DCI transmitted by gNBcan be used, for example, for conveying downlink (DL) and uplink (UL)scheduling information to a UE. For example, certain embodiments relateto PDCCH blind detection arrangement in the case when the UE isoperating in DRX mode. This mode targeting minimization of UE powerconsumption may or may not involve dynamically varying RF bandwidth.

One of the issues related to LTE is that conventionally UE needs toconstantly monitor PDCCH covering the entire DL carrier bandwidth.Certain embodiments provide some practical enablers for improvedoperation for PDCCH-only and low data services in the NR.

In certain embodiments, a UE can be configured with two or more searchspace configurations. The two example configurations described below aredesignated configuration (also referred to herein as “config”) A andconfiguration B, merely for convenience and ease of reference, and notby way of limitation.

Configuration A can correspond to search space configuration for thecase when UE is having active data transmission. This may be a casewhen, for example, a UE is neither in the “DRX” nor in the “low datarate service” mode, if supported. This configuration can becharacterized by one or more of the following attributes: searchspace(s) cover a wide bandwidth; search space(s) cover a high number ofCCEs; UE operates with a high number of PDCCH blind decoding attemptsper slot or per mini-slot (or per subframe); UE is monitoring allrequired PDCCH from both slots and mini-slots; UE is operating withradio frequency (RF) bandwidth up to a bandwidth corresponding tomaximum channel bandwidth; and UE has a large data volume in at leastone link direction, either DL or UL.

Configuration B can correspond to search space configuration for thecase when UE is operating, for example according to a DRX mode or onlyhaving limited data service ongoing. This configuration can becharacterized by one or more of the following attributes: searchspace(s) cover a narrow bandwidth; search space(s) cover a low number ofCCEs; UE operates with a low number of PDCCH blind decoding; UE ismonitoring PDCCH at maximum with slot resolution at least in DRX mode;UE is operating with RF bandwidth corresponding to a subset of themaximum channel bandwidth; and UE is supporting a limited data volume inat least in at least one link direction, either DL or UL.

The switching between the different configurations, in this examplebetween configuration A and configuration B, can be based on switchingfrom narrow bandwidth (BW) to wider BW or from wider BW to lower BW.

In the case of switching from narrow BW to wider BW, the gNB canindicate to the UE explicitly which configuration to use. This may bedone using LI DL control signaling (such as DCI) or a medium accesscontrol (MAC) control element (CE). The gNB may provide suitablereference signal (RS) resources for frequency/time synchronization andautomatic gain control at the UE. Another form of configurationindication is implicit signaling, in which the UE is allocated resourcescorresponding to a wider BW. Alternatively, if the UE has a CSS specificconfiguration (e.g. configuration B) and UE is allocated resources, theUE can switch to another configuration, such as configuration A.

Switching from wider bandwidth to lower bandwidth could be based on thegNB indicating to the UE explicitly which configuration to use.Alternatively, the switching could be based on timer procedures, such aswhen a certain predefined amount of time has passed.

Thus, in certain embodiments, the UE may have at least two USSconfigurations defined by higher layer signaling. The first USSconfiguration can be used when the UE is operating according toconfiguration A. The second USS configuration can be used when the UE isoperating according to configuration B.

In one embodiment, when operating according to configuration B, the UEmay follow only a PDCCH common search space. In another embodiment, theCSS can be defined according to configuration B. For example, the CSScan be configured according to a certain maximum bandwidth. Maximum CSSbandwidth may cover at maximum X MHz when operating at a certainfrequency band. For example, X could be ˜5 MHz when operating infrequency bands smaller or equal than, e.g., 6 GHz.

In yet another embodiment, configuration B may contain onlypredetermined PDCCH aggregation levels, which may, in turn, limit thenumber of PDCCH blind decoding attempts. For example, when operatingaccording to configuration A, the UE may follow all PDCCH aggregationlevels (e.g., AL=1, AL=2, AL=4, AL=8), while when operating according toconfiguration B, the UE may follow PDCCH aggregation levels (AL)≥4.

In one possible embodiment, configuration A and configuration B can alsobe used by the network to reduce the power consumption dynamically, bylimiting the required transmission of the gNB correspondingly.

In certain embodiments, both CSS and USS(s) can be configured via higherlayer signaling. CSS configuration may be cell specific or UE groupspecific. USS configuration(s) may be defined based on dedicated RRCsignaling.

FIG. 4 illustrates examples of CSS/USS configurations for configurationA and configuration B, according to certain embodiments. As illustratedin FIG. 4 , configuration A can include CSS with four CCEs arranged in adistributed manner, and USS 10 CCEs arranged in a localized manner,respectively. Bandwidth allocation covers 80 physical resource blocks(PRBs) in total. By contrast, configuration B can include CSS with fourCCEs arranged in a distributed manner, and USS with four CCEs arrangedin a localized manner. Bandwidth allocation covers 32 PRBs in total.Although example shown in FIG. 4 covers only one carrier, the principlecan also be extended to cover carrier aggregation and other bandwidthextension schemes.

In general, there could be more than two configurations. The differentconfigurations could be used according to need for bandwidth, whichcould be due to, for example, high data rates, load balancing, or thelike. For instance the bandwidth could be adjusted based on the instantdata throughput needs such that when there is need for high TP theconfiguration using, for example, the full available bandwidth would beused while when the data TP need is lower a configuration using, forexample, half the available bandwidth could be used. This adaptation ofused configurations could be flexible and done on the fly based on, forexample, TP need.

FIG. 5 illustrates a method according to certain embodiments. As shownin FIG. 5 , a method can include, at 510, selecting a search spaceconfiguration from a plurality of search space configurations for a userequipment. The plurality of search space configurations can respectivelycover at least two different bandwidths. For example a firstconfiguration can cover a first bandwidth and a second configuration cancover a second bandwidth that is different from the first bandwidth. Themethod can also include, at 520, operating the user equipment in theselected search space configuration. The operating of the user equipmentcan include performing physical downlink control channel blinddetection.

The method can further include, at 530, switching between search spaceconfiguration.

The selecting at 510 and/or the switching at 530 can be based on needfor bandwidth. The switching at 530 can also or alternatively be basedon the expiration of a timer. The selecting at 510 and/or the switchingat 530 can be based on an explicit or implicit indication received froman access node at 507 and/or an access node at 527. Switching caninvolve, for example, switching from configuration A to configuration Bor from configuration B to configuration A. Switching from configurationB to configuration A may require an additional synchronization signal.Whereas switching from configuration A to configuration B can rely on atimer and can be combined with a discontinuous reception procedure.

The method can further include receiving, at 505, configuration of theplurality search space configurations by higher layer signaling.

The plurality of search space configurations can be variously divided.For example, the plurality of search space configurations can include afirst search space configuration configured to support a user equipmentin active data transmission and a second search space configurationconfigured to support a user equipment in discontinuous reception modeor in a low data rate service mode.

For another example, the plurality of search space configurations caninclude a first search space configuration configured to cause the userequipment to follow all physical downlink control channel aggregationlevels and a second search space configuration configured to cause theuser equipment to follow only a subset of physical downlink controlchannel aggregation levels.

For a further example, the plurality of search space configurations caninclude a first search space configuration configured to cause the userequipment to follow both a common search space and a user specificsearch space and a second search space configuration configured to causethe user equipment to follow only a common search space. In anotheralternative, one or more of the plurality of search space configurationscan configure the user equipment only to follow a user specific searchspace.

In certain embodiments, the plurality of search space configurations caninclude different user specific search spaces from one another.

The above features of the method may be performed by a device such as auser equipment. The following features of the method may be performed byanother device, such as an access node, for example a next generationNodeB (gNB).

The method can include, at 540, selecting a search space configurationfrom a plurality of search space configurations for a user equipment.The method can also include, at 550, indicating to the user equipmentthe selected search space configuration. This can be the same indicationreceived at UE, at 507. The method can also include, at 560, sending anindication to the user equipment to switch to a different search spaceconfiguration of the plurality of search space configurations. This canbe the same indication received at UE, at 527. The method can alsoinclude sending, at 570, a configuration of the plurality of searchspace configurations. This configuration can be the same configurationreceived at UE, at 505.

FIG. 6 illustrates a system according to certain embodiments of theinvention. It should be understood that each block of the flowchart ofFIG. 5 may be implemented by various means or their combinations, suchas hardware, software, firmware, one or more processors and/orcircuitry. In one embodiment, a system may include several devices, suchas, for example, network element 610 and user equipment (UE) or userdevice 620. The system may include more than one UE 620 and more thanone network element 610, although only one of each is shown for thepurposes of illustration. A network element can be an access point, abase station, an eNodeB (eNB), a gNB, or any other network element.

Each of these devices may include at least one processor or control unitor module, respectively indicated as 614 and 624. At least one memorymay be provided in each device, and indicated as 615 and 625,respectively. The memory may include computer program instructions orcomputer code contained therein, for example for carrying out theembodiments described above. One or more transceiver 616 and 626 may beprovided, and each device may also include an antenna, respectivelyillustrated as 617 and 627. Although only one antenna each is shown,many antennas and multiple antenna elements may be provided to each ofthe devices. Other configurations of these devices, for example, may beprovided. For example, network element 610 and UE 620 may beadditionally configured for wired communication, in addition to wirelesscommunication, and in such a case antennas 617 and 627 may illustrateany form of communication hardware, without being limited to merely anantenna.

Transceivers 616 and 626 may each, independently, be a transmitter, areceiver, or both a transmitter and a receiver, or a unit or device thatmay be configured both for transmission and reception. The transmitterand/or receiver (as far as radio parts are concerned) may also beimplemented as a remote radio head which is not located in the deviceitself, but in a mast, for example. It should also be appreciated thataccording to the “liquid” or flexible radio concept, the operations andfunctionalities may be performed in different entities, such as nodes,hosts or servers, in a flexible manner. In other words, division oflabor may vary case by case. One possible use is to make a networkelement to deliver local content. One or more functionalities may alsobe implemented as a virtual application that is provided as softwarethat can run on a server.

A user device or user equipment 620 may be a mobile station (MS) such asa mobile phone or smart phone or multimedia device, a computer, such asa tablet, provided with wireless communication capabilities, personaldata or digital assistant (PDA) provided with wireless communicationcapabilities, vehicle, portable media player, digital camera, pocketvideo camera, navigation unit provided with wireless communicationcapabilities or any combinations thereof. The user device or userequipment 620 may be a sensor or smart meter, or other device that mayusually be configured for a single location.

In an exemplifying embodiment, an apparatus, such as a node or userdevice, may include means for carrying out embodiments described abovein relation to FIG. 5 .

Processors 614 and 624 may be embodied by any computational or dataprocessing device, such as a central processing unit (CPU), digitalsignal processor (DSP), application specific integrated circuit (ASIC),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), digitally enhanced circuits, or comparable device or acombination thereof. The processors may be implemented as a singlecontroller, or a plurality of controllers or processors. Additionally,the processors may be implemented as a pool of processors in a localconfiguration, in a cloud configuration, or in a combination thereof.The term circuitry may refer to one or more electric or electroniccircuits. The term processor may refer to circuitry, such as logiccircuitry, that responds to and processes instructions that drive acomputer.

For firmware or software, the implementation may include modules orunits of at least one chip set (e.g., procedures, functions, and so on).Memories 615 and 625 may independently be any suitable storage device,such as a non-transitory computer-readable medium. A hard disk drive(HDD), random access memory (RAM), flash memory, or other suitablememory may be used. The memories 615, 625 may be combined on a singleintegrated circuit as the processor, or may be separate therefrom.Furthermore, the computer program instructions may be stored in thememory and which may be processed by the processors can be any suitableform of computer program code, for example, a compiled or interpretedcomputer program written in any suitable programming language. Thememory or data storage entity is typically internal but may also beexternal or a combination thereof, such as in the case when additionalmemory capacity is obtained from a service provider. The memory 615, 625may be fixed or removable.

The memory 615, 625 and the computer program instructions may beconfigured, with the processor 614, 624 for the particular device, tocause a hardware apparatus such as network element 610 and/or UE 620, toperform any of the processes described above (see, for example, FIG. 5). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions or one or morecomputer program (such as added or updated software routine, applet ormacro) that, when executed in hardware, may perform a process such asone of the processes described herein. Computer programs may be coded bya programming language, which may be a high-level programming language,such as objective-C, C, C++, C#, Java, etc., or a low-level programminglanguage, such as a machine language, or assembler. Alternatively,certain embodiments of the invention may be performed entirely inhardware.

Furthermore, although FIG. 6 illustrates a system including a networkelement 610 and a UE 620, embodiments of the invention may be applicableto other configurations, and configurations involving additionalelements, as illustrated and discussed herein. For example, multipleuser equipment devices and multiple network elements may be present, orother nodes providing similar functionality, such as nodes that combinethe functionality of a user equipment and an access point, such as arelay node.

Certain embodiments may have various benefits and/or advantages. Forexample, certain embodiments may provide for reduced UE powerconsumption when operating in a DRX mode. Additionally, certainembodiments may permit adaptation of bandwidth usage based on need.Thus, certain embodiments may permit scalable UE power consumption,scalable gNB transmission BW, and reduced interference. Certainembodiments can leverage DRX functionalities for bandwidth adaptation(both within carrier and in combination with carrier aggregation).Additionally, certain embodiments may provide that RF bandwidthadaptation can be based on actual instant need, for example, data TPneed and when operating in DRX mode.

One having ordinary skill in the art will readily understand that theinvention as discussed above may be practiced with steps in a differentorder, and/or with hardware elements in configurations which aredifferent than those which are disclosed. Therefore, although theinvention has been described based upon these preferred embodiments, itwould be apparent to those of skill in the art that certainmodifications, variations, and alternative constructions would beapparent, while remaining within the spirit and scope of the invention.

LIST OF ABBREVIATIONS

NR New Radio

DRX Discontinuous Reception

DCI Downlink Control Information

RF Radio Frequency

PDCCH Physical Downlink Control Channel

TDD Time Division Duplexing

DL Downlink

UL Uplink

GP Guard Period

EPDCCH Enhanced PDCCH

CCE Control Channel Element

LTE Long Term Evolution

cc Component Carrier

PRB Physical Resource Block

CSS Common Search Space

uss User specific Search Space

BW Bandwidth

According to a first embodiment, a method can include selecting a searchspace configuration from a plurality of search space configurations fora user equipment. The method can also include operating the userequipment in the selected search space configuration. The plurality ofsearch space configurations can respectively cover at least twodifferent bandwidths.

In a variant, the method can further include switching between searchspace configuration.

In a variant, the selecting can be based on need for bandwidth.

In a variant, the switching can be based on a change in need forbandwidth.

In a variant, the switching can be based on the expiration of a timer.

In a variant, the selecting can be based on an explicit indication froman access node.

In a variant, the switching can including switching from configuration Ato configuration B or switching from configuration B to configuration A.

In a variant, the method can further comprise relying on an additionalsynchronization signal when switching from configuration B toconfiguration A.

In a variant the method can comprising relying on a timer when switchingfrom configuration A to configuration B.

In a variant, configuration A can have one or more of the followingattributes: search space(s) cover a wide bandwidth; search space(s)cover a high number of control channel elements; user equipment operateswith a high number of physical downlink control channel blind decodingattempts per slot or per mini-slot (or per subframe); user equipment ismonitoring all required physical downlink control channel from bothslots and mini-slots; user equipment is operating with radio frequencybandwidth up to a bandwidth corresponding to maximum channel bandwidth;or user equipment has a large data volume in at least one linkdirection, either downlink or uplink.

In a variant, configuration B can have one or more of the followingattributes: search space(s) cover a narrow bandwidth; search space(s)cover a low number of control channel elements; user equipment operateswith a low number of physical downlink control channel blind decoding;user equipment is monitoring physical downlink control channel atmaximum with slot resolution at least in discontinuous reception mode;user equipment is operating with radio frequency bandwidth correspondingto a subset of the maximum channel bandwidth; or user equipment issupporting a limited data volume in at least in at least one linkdirection, either downlink or uplink.

In a variant, the switching can be based on an explicit indication froman access node.

In a variant, the plurality of search space configurations can include afirst search space configuration configured to support a user equipmentin active data transmission.

In a variant, the plurality of search space configurations can include asecond search space configuration configured to support a user equipmentin discontinuous reception mode or in a low data rate service mode.

In a variant, the method can further include receiving configuration ofthe plurality search space configurations by higher layer signaling.

In a variant, the plurality of search space configurations can include afirst search space configuration configured to cause the user equipmentto follow all physical downlink control channel aggregation levels.

In a variant, the plurality of search space configurations can include asecond search space configuration configured to cause the user equipmentto follow only a subset of physical downlink control channel aggregationlevels.

In a variant, the plurality of search space configurations can include afirst search space configuration configured to cause the user equipmentto follow both a common search space and a user specific search space.

In a variant, the plurality of search space configurations can include asecond search space configuration configured to cause the user equipmentto follow only a common search space.

In a variant, the plurality of search space configurations can includedifferent user specific search spaces from one another.

In a variant, the operating of the user equipment can include performingphysical downlink control channel blind detection.

According to a second embodiment, a method can include selecting asearch space configuration from a plurality of search spaceconfigurations for a user equipment. The method can also includeindicating to the user equipment the selected search spaceconfiguration. The plurality of search space configurations canrespectively cover at least two different bandwidths.

In a variant, the method can also include sending an indication to theuser equipment to switch to a different search space configuration ofthe plurality of search space configurations.

The second embodiment can also include any of the variants of the firstembodiment.

According to third and fourth embodiments, an apparatus can includemeans for performing the method according to the first and secondembodiments respectively, in any of their variants.

According to fifth and sixth embodiments, an apparatus can include atleast one processor and at least one memory including computer programcode. The at least one memory and the computer program code can beconfigured to, with the at least one processor, cause the apparatus atleast to perform the method according to the first and secondembodiments respectively, in any of their variants.

According to seventh and eighth embodiments, a computer program productmay encode instructions for performing a process including the methodaccording to the first and second embodiments respectively, in any oftheir variants.

According to ninth and tenth embodiments, a non-transitory computerreadable medium may encode instructions that, when executed in hardware,perform a process including the method according to the first and secondembodiments respectively, in any of their variants.

According to eleventh and twelfth embodiments, a system may include atleast one apparatus according to the third or fifth embodiments incommunication with at least one apparatus according to the fourth orsixth embodiments, respectively in any of their variants.

1. An apparatus comprising: at least one processor; and at least onememory including computer program code, wherein the at least one memoryand the computer program code are configured to, with the at least oneprocessor, cause the apparatus at least to perform: selecting a searchspace configuration from a plurality of search space configurations fora user equipment; and operating the user equipment in the selectedsearch space configuration, wherein the plurality of search spaceconfigurations can respectively cover at least two different bandwidths.2. The apparatus according to claim 1, wherein the at least one memoryand the computer program code are further configured to, with the atleast one processor, cause the apparatus at least to perform: switchingbetween search space configurations.
 3. The apparatus according to claim1, wherein the selecting is based on at least one of need for bandwidthor based on an explicit indication from an access node.
 4. The apparatusaccording to claim 2, wherein the switching is based on at least one ofa change in need for bandwidth, an expiration of a timer, or an explicitindication from an access node.
 5. The apparatus according to claim 2,wherein the switching comprises switching from configuration A toconfiguration B or switching from configuration B to configuration A. 6.The apparatus according to claim 5, wherein the at least one memory andthe computer program code are further configured to, with the at leastone processor, cause the apparatus at least to perform: relying on atimer when switching from the configuration A to the configuration B, orrelying on an additional synchronization signal when switching from theconfiguration B to the configuration A.
 7. The apparatus according toclaim 5, wherein the configuration A comprises one or more of thefollowing attributes: search space(s) covering a wide bandwidth; searchspace(s) covering a high number of control channel elements; userequipment operating with a high number of physical downlink controlchannel blind decoding attempts per slot or per mini-slot or persubframe; user equipment monitoring all required physical downlinkcontrol channel from both slots and mini-slots; user equipment operatingwith radio frequency bandwidth up to a bandwidth corresponding tomaximum channel bandwidth; or user equipment having a large data volumein at least one link direction, either downlink or uplink.
 8. Theapparatus according to claim 5, wherein the configuration B comprisesone or more of the following attributes: search space(s) covering anarrow bandwidth; search space(s) covering a low number of controlchannel elements; user equipment operating with a low number of physicaldownlink control channel blind decoding; user equipment monitoringphysical downlink control channel at maximum with slot resolution atleast in discontinuous reception mode; user equipment operating withradio frequency bandwidth corresponding to a subset of the maximumchannel bandwidth; or user equipment supporting a limited data volume inat least in at least one link direction, either downlink or uplink. 9.The apparatus according to claim 1, wherein the plurality of searchspace configurations comprise at least one of a first search spaceconfiguration configured to support the user equipment in active datatransmission, a second search space configuration configured to supportthe user equipment in discontinuous reception mode or in a low data rateservice mode.
 10. The apparatus according to claim 1, wherein the atleast one memory and the computer program code are further configuredto, with the at least one processor, cause the apparatus at least toperform: receiving configuration of the plurality search spaceconfigurations by higher layer signaling.
 11. The apparatus according toclaim 1, wherein the plurality of search space configurations compriseat least one of a first search space configuration configured to causethe user equipment to follow all physical downlink control channelaggregation levels, a second search space configuration configured tocause the user equipment to follow only a subset of physical downlinkcontrol channel aggregation levels, a first search space configurationconfigured to cause the user equipment to follow both a common searchspace and a user specific search space, a second search spaceconfiguration configured to cause the user equipment to follow only acommon search space, or different user specific search spaces from oneanother.
 12. The apparatus according to claim 1, wherein the operatingof the user equipment comprises performing physical downlink controlchannel blind detection.
 13. An apparatus comprising: at least oneprocessor; and at least one memory including computer program code,wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus atleast to perform: selecting a search space configuration from aplurality of search space configurations for a user equipment; andindicating, to the user equipment, the selected search spaceconfiguration, wherein the plurality of search space configurationsrespectively cover at least two different bandwidths.
 14. The apparatusaccording to claim 13, wherein the at least one memory and the computerprogram code are further configured to, with the at least one processor,cause the apparatus at least to perform: sending an indication to theuser equipment to switch to a different search space configuration ofthe plurality of search space configurations.
 15. The apparatusaccording to claim 13, wherein the selecting is based on at least one ofneed for bandwidth.
 16. The apparatus according to claim 14, wherein theswitching is based on at least one of a change in need for bandwidth,the expiration of a timer.
 17. The apparatus according to claim 14,wherein the switching comprises switching from configuration A toconfiguration B or switching from configuration B to configuration A.18. The apparatus according to claim 17, wherein the at least one memoryand the computer program code are further configured to, with the atleast one processor, cause the apparatus at least to perform: relying ona timer when switching from the configuration A to the configuration B,or relying on an additional synchronization signal when switching fromthe configuration B to the configuration A.
 19. The apparatus accordingto claim 17, wherein the configuration A comprises one or more of thefollowing attributes: search space(s) covering a wide bandwidth; searchspace(s) covering a high number of control channel elements; userequipment operating with a high number of physical downlink controlchannel blind decoding attempts per slot or per mini-slot or persubframe; user equipment monitoring all required physical downlinkcontrol channel from both slots and mini-slots; user equipment operatingwith radio frequency bandwidth up to a bandwidth corresponding tomaximum channel bandwidth; or user equipment having a large data volumein at least one link direction, either downlink or uplink.
 20. Theapparatus according to claim 17, wherein the configuration B comprisesone or more of the following attributes: search space(s) covering anarrow bandwidth; search space(s) covering a low number of controlchannel elements; user equipment operating with a low number of physicaldownlink control channel blind decoding; user equipment monitoringphysical downlink control channel at maximum with slot resolution atleast in discontinuous reception mode; user equipment operating withradio frequency bandwidth corresponding to a subset of the maximumchannel bandwidth; or user equipment supporting a limited data volume inat least in at least one link direction, either downlink or uplink.